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The γ-tubulin ring complex (γ-TuRC) is an essential regulator of centrosomal and acentrosomal microtubule formation, yet its structure is not known. Here, we present a cryo-EM reconstruction of the native human γ-TuRC at ∼3.8 Å resolution, revealing an asymmetric, cone-shaped structure. Pseudo-atomic models indicate that GCP4, GCP5, and GCP6 form distinct Y-shaped assemblies that structurally mimic GCP2/GCP3 subcomplexes distal to the γ-TuRC "seam." We also identify an unanticipated structural bridge that includes an actin-like protein and spans the γ-TuRC lumen. Despite its asymmetric architecture, the γ-TuRC arranges γ-tubulins into a helical geometry poised to nucleate microtubules. Diversity in the γ-TuRC subunits introduces large (>100,000 Å2) surfaces in the complex that allow for interactions with different regulatory factors. The observed compositional complexity of the γ-TuRC could self-regulate its assembly into a cone-shaped structure to control microtubule formation across diverse contexts, e.g., within biological condensates or alongside existing filaments. • High resolution cryo-EM structure of the native human γ-tubulin ring complex (γ-TuRC) • Identification and structural models for γ-tubulin, GCP2, GCP3, GCP4, GCP5, and GCP6 • Identification of an actin-like protein in the γ-TuRC lumen • Insights into the regulation of microtubule nucleation by the γ-TuRC A high resolution cryo-EM reconstruction of the cell's microtubule nucleating machinery reveals an unusual cone-shaped structure. [ABSTRACT FROM AUTHOR]